The present invention relates to the field of orthodontics, that is to say, that branch of dentistry concerned with correcting and preventing irregularities of the teeth so as to bring about proper occlusion. Maloccluded teeth may be straightened by the provision of a horizontal arch wire, anchored at each end to suitable anchor teeth, such as molars, and held in a horizontal disposition by means of brackets connected to appropriate teeth. One such well known straightening method is the Begg Light Wire Technique (see "American Journal of Orthodontics," volume 42, No. 7 July 1956 page 48). In this method there is employed an orthodontic bracket formed of metal and comprising base and top portions, with the under surface of the base welded to a band which, in use, embraces the tooth and the top being provided with means -- for instance, one or more closable slots -- for accommodating the arch wire.
The orthodontic brackets of the Begg type are, however, not particularly suitable for straightening the teeth in a mesiodistal direction (that is, toward and away from the midpoint and endpoints of the dental arch) as there is insufficient provision for the arch wire to pivot in relation to the bracket as the tooth is displaced mesiodistally.
U.S. Pat. No. 3,408,739 filed Apr. 18, 1966 by Frank W. Johnston for "Orthodontic Bracket" attempts to overcome this problem by providing an orthodontic bracket with an integral pivotal edge to support the light arch wire. The bracket includes an occulusalgingivally extending channel to receive a lock pin for securing the light arch wire against the pivotal edge. The pivotal edge of the Johnston bracket provides two single points of contact for the arch wire. This two-point contact has, however, been found in practice to tend to displace the tooth in an occulusalgingival direction and thus the effectiveness of the bracket is considerably reduced.
In practice, however, the pivotal edge on Johnston's bracket tends to weaken the wire at the point of contact therewith so that in prolonged use there is a stretching of the wire and loss of efficiency. Also, there is a tendency for the wire to "catch" on the edge and thus hinder the mesiodistal displacement of the tooth.
It is therefore an object of the present invention to provide an orthodontic bracket which permits mesiodistal tipping of a maloccluded tooth and which does not have the aforementioned disadvantages of the Begg and Johnston brackets.
Orthodontic brackets in common use are attached to the teeth either by metal tooth embracing bands or cement. Tooth embracing bands are cumbersome, less hygienic and have poorer aesthetics in use while cements have the common disadvantage that they are either suitable for specifically adhering to the tooth, or the bracket material, but not both.
It is therefore a further object of the present invention to provide an orthodontic bracket which is usable with cements which are specifically suitable for adhering to teeth only.